Diana Lombard is the deuteragonist of the animated series, Martin Mystery, and his stepsister. She usually turns hot-tempered whenever Martin would do something foolish.
She is voiced by Kelly Sheridan, who also formerly voiced Barbie.
Diana's appearance was shown as a slender Caucasian female, with two signature purple hair clips on them and dark green eyes. Also, her main outfit is a long sleeve pink shirt with dark pink sleeves, light blue jeans that stop at her knees and pink and white sneakers with no socks in them. Also, she is usually seen with her small purple shoulder bag.
Diana is at times quite jumpy and squeamish on missions, but shows great courage when called on. Not sharing Martin's love of the paranormal, she often tries to explain something with logic before it becomes apparently paranormal.
Diana has the hardest time keeping her cool and temper with Martin and will generally slap, kick, beat or scream at him quite often with physical abuse. Regardless of Martin's quirky and hyperactive behavior, she loves him like her own real brother.
- Her physical appearance and personality are similar to another character, Sam from Totally Spies!.
- She is the love interest of Martin in the comics.
- Her Voice Actress, Kelly Sheridan is best known for voicing Barbie from Barbie movie series, Sango from InuYasha/The Final Act, Ukyo Kuonji from Ranma ½, Mammoth Mutt from Krypto the Superdog, Starlight Glimmer from My Little Pony: Friendship is Magic, Surprise Bear from Care Bears: Adventures in Care-a-Lot, Nikki from Cardcaptors, Indigo Zap from My Little Pony: Equestria Girls: Friendship Games, Cheerilee from My Little Pony: Pinkie Pie's Special Day through My Little Pony: Twinkle Wish Adventure and Cotton Candy from My Little Pony: A Charming Birthday through My Little Pony Crystal Princess: The Runaway Rainbow.